Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h,w=map(int,input().split())
cnt=0
s=[input() for _ in range(h)]
for x in s:
	cnt+=x.count(".")
ans=0
inf=10**8
dp=[[inf]*w for _ in range(h)]
dp[0][0]=0
from collections import deque
queue=deque([(0,0)])
d=((0,1),(0,-1),(1,0),(-1,0))
while queue:
	r=queue.popleft()
	for x in d:
		xx=r[0]+x[0];yy=r[1]+x[1]
		if 0<=xx<h and 0<=yy<w:
			if s[xx][yy]=="." and dp[xx][yy]==inf:
				dp[xx][yy]=dp[r[0]][r[1]]+1
				queue.append((xx,yy))
if dp[-1][-1]==inf:
	print(-1)
	exit()
print(cnt-dp[-1][-1]-1)